The traditional solution, which uses a length of intestine to reconstruct the bladder, is fraught with complications, including urinary tract infections, metabolic abnormalities, bladder stones and, most alarmingly, a heightened risk for bladder cancer. “This surgery has been used for 40 years,” says Children’s Hospital Boston urologist Carlos Estrada, MD. “But every time I do one I say, there has to be something better.”

That “something better” may be bladders made from the induced pluripotent stem cells (iPS cells) growing in a freezer in Estrada’s lab. Already, he has successfully converted mouse ESs and iPS cells into the bladder’s smooth muscle cells and the specialized epithelial cells that line the bladder. The experiments worked so well that Estrada at first thought his results were false—in just nine days, he had cells expressing the full range of proteins found exclusively in bladder epithelium. He hopes to repeat this success in human iPS cells.